A passenger elevator and freight elevator generally comprise one or more moving doors. The moving doors are on the floor levels and in the elevator car.
When a moving door closes, the opening of the door in question decreases in size. For the sake of safety, the aperture must be monitored. A moving door that is closing must be stopped or its movement must be slowed down when a penetration into the opening is detected. In this way it is possible to prevent damage to life, health and property being caused by a moving door.
Section 5.3.6 of the European Standard prEN 81-20:2011-11 “Safety rules for the construction and installation of lifts” defines more precise requirements for how the opening of a moving door must be monitored. The standard in question is based on European Parliament and Council Directive 95/16/EC on the approximation of the laws of the Member States relating to lifts, which describes the requirements to be set for new electrically-operated passenger elevators and freight elevators in the European Economic Area.
A light curtain is generally used to monitor the opening of a moving door. Airdri Limited's patent publications U.S. Pat. No. 6,547,042 (published also EP 1 212 506 B1), GB 2 395 474 A, US 2004/0154873 A1 and WO 2005/110906 A2 present some technical solutions used in light curtains intended for monitoring an opening of a moving door of elevators.
Patent publication WO 2005/110906 A2 presents a way of connecting the control unit of a light curtain using a cable to an operating system for opening and closing a door and also, on the other hand, along a link to the operating system of the elevator roping.